Search

We have compiled a large dataset of peat and soil cores from temperate and boreal regions of eastern Canada to develop a simple field method for estimating the mass of soil organic carbon (SOC) stored in undisturbed wetlands (peatlands, swamps and marshes). We show that it is possible to predict the SOC mass in different wetland types by measuring the organic-rich soil layer thickness in the field. Using this new dataset, we found that SOC mass can be estimated either by using the linear regression equation between peat or soil thickness and SOC mass or by multiplying peat or soil thickness by a mean SOC density. We also show that SOC mass can be estimated by determining the degree of peat humification in the northern peatlands investigated. In this dataset, the precision of estimates is higher for peatlands than mineral wetlands (marshes and swamps), mainly due to the lack of empirical soil core data. The simple approach proposed here could be applied in different wetland regions worldwide where carbon density data from soil cores are available. This cost- and time-efficient method could benefit regional or national-scale carbon inventories.

A recent synthesis study found 54% of the high-latitude peatlands have been drying and 32% have been wetting over the past centuries, illustrating their complex ecohydrological dynamics and highly uncertain responses to a warming climate.

Abstract Background Black spruce (Picea mariana (Mill.) BSP)-forested peatlands are widespread ecosystems in boreal North America in which peat accumulation, known as the paludification process, has been shown to induce forest growth decline. The continuously evolving environmental conditions (e.g., water table rise, increasing peat thickness) in paludified forests may require tree growth mechanism adjustments over time. In this study, we investigate tree ecophysiological mechanisms along a paludification gradient in a boreal forested peatland of eastern Canada by combining peat-based and tree-ring analyses. Carbon and oxygen stable isotopes in tree rings are used to document changes in carbon assimilation rates, stomatal conductance, and water use efficiency. In addition, paleohydrological analyses are performed to evaluate the dynamical ecophysiological adjustments of black spruce trees to site-specific water table variations. Results Increasing peat accumulation considerably impacts forest growth, but no significant differences in tree water use efficiency (iWUE) are found between the study sites. Tree-ring isotopic analysis indicates no iWUE decrease over the last 100 years, but rather an important increase at each site up to the 1980s, before iWUE stabilized. Surprisingly, inferred basal area increments do not reflect such trends. Therefore, iWUE variations do not reflect tree ecophysiological adjustments required by changes in growing conditions. Local water table variations induce no changes in ecophysiological mechanisms, but a synchronous shift in iWUE is observed at all sites in the mid-1980s. Conclusions Our study shows that paludification induces black spruce growth decline without altering tree water use efficiency in boreal forested peatlands. These findings highlight that failing to account for paludification-related carbon use and allocation could result in the overestimation of aboveground biomass production in paludified sites. Further research on carbon allocation strategies is of utmost importance to understand the carbon sink capacity of these widespread ecosystems in the context of climate change, and to make appropriate forest management decisions in the boreal biome.

Abstract Peatlands are significant carbon (C) stores, playing a key role in nature-based climate change mitigation. While the effectiveness of non-forested peatlands as C reservoirs is increasingly recognized, the C sequestration function of forested peatlands remains poorly documented, despite their widespread distribution. Here, we evaluate the C sequestration potential of pristine boreal forested peatlands over both recent and millennial timescales. C stock estimates reveal that most of the carbon stored in these ecosystems is found in organic horizons (22.6–66.0 kg m−2), whereas tree C mass (2.8–5.7 kg m−2) decreases with thickening peat. For the first time, we compare the boreal C storage capacities of peat layers and tree biomass on the same timescale, showing that organic horizons (11.0–12.6 kg m−2) can store more carbon than tree aboveground and belowground biomass (2.8–5.7 kg m−2) even over a short time period (last 200 years). We also show that forested peatlands have similar recent rates of C accumulation to boreal non-forested peatlands but lower long-term rates, suggesting higher decay and more important peat layer combustion during fire events. Our findings highlight the significance of forested peatlands for C sequestration and suggest that greater consideration should be given to peat C stores in national greenhouse gas inventories and conservation policies.

Global warming could increase climatic instability and large wildfire activity in circumboreal regions, potentially impairing both ecosystem functioning and human health. However, links between large wildfire events and climatic and/or meteorological conditions are still poorly understood, partly because few studies have covered a wide range of past climate-fire interactions. We compared palaeofire and simulated climatic data over the last 7000 years to assess causes of large wildfire events in three coniferous boreal forest regions in north-eastern Canada. These regions span an east-west cline, from a hilly region influenced by the Atlantic Ocean currently dominated by Picea mariana and Abies balsamea to a flatter continental region dominated by Picea mariana and Pinus banksiana . The largest wildfires occurred across the entire study zone between 3000 and 1000 cal. BP. In western and central continental regions these events were triggered by increases in both the fire-season length and summer/spring temperatures, while in the eastern region close to the ocean they were likely responses to hydrological (precipitation/evapotranspiration) variability. The impact of climatic drivers on fire size varied spatially across the study zone, confirming that regional climate dynamics could modulate effects of global climate change on wildfire regimes.

Ante-mortem diagnosis of bovine tuberculosis (bTB) is based mainly on the tuberculin skin test (TST) and the ɣ-IFN release assay (IGRA). Some infected animals escape screening tests, thus, limit herd sanitation. Previous reports have suggested a predominant pattern of multi-organ lesions attributable to Mycobacterium bovis (the causative agent of bTB) bacteraemia. A case–control study was conducted to investigate blood PCR as an alternative tool for improving ante-mortem detection of TST false-negative bovines. Cases comprised 70 TST false-negative bovines (cases), which were serology positive, and controls included 81 TST positive bovines; all of them confirmed as infected with M. bovis. Detection of the IS6110 target through touchdown blood-PCR (IS6110 TD-PCR) was performed. The positivity of the blood-PCR was 27.2% in the control group. This performance was similar to the 15% obtained among cases (p = 0.134). Most cases identified by the IS6110 TD-PCR exhibited focalized lesions (p = 0.002). Results demonstrated that blood-PCR could detect TST false-negative cattle, even if they are negative for IGRA. Considering that cases exhibited humoral response to M. bovis, further studies conducted in a pre-serological stage could provide evidence about the real contribution of the technique in herds.

En tuberculosis, el conocimiento de los diferentes tipos de lesiones, permite comprender con mayor profundidad la patología y el contagio de la enfermedad. Las cabras tienen un rol importante en transmitir esta afección a bovinos y a humanos. El objetivo del presente trabajo es describir las lesiones macroscópicas y microscópicas observadas en cabras naturalmente infectadas con Mycobacterium bovis (M. bovis). Se analizaron 55 caprinos positivos a la prueba de tuberculina, detallando las diferentes presentaciones patológicas macroscópicas y microscópicas. Entre ellas se encontraron 5 animales con lesiones cavitarias pulmonares. Se concluye que, en cabras infectadas naturalmente, existe una amplia variedad de lesiones, afectando principalmente el sistema respiratorio; algunas de ellas involucradas muy directamente con la trasmisión de la enfermedad dentro de los hatos.

Mycobacterium bovis is the causative agent of bovine tuberculosis (TB), a disease that affects approximately 5% of Argentinean cattle. Among the molecular methods for genotyping, the most convenient are spoligotyping and variable number of tandem repeats (VNTR). A total of 378 samples from bovines with visible lesions consistent with TB were collected at slaughterhouses in three provinces, yielding 265 M. bovis spoligotyped isolates, which were distributed into 35 spoligotypes. In addition, 197 isolates were also typed by the VNTR method and 54 combined VNTR types were detected. There were 24 clusters and 27 orphan types. When both typing methods were combined, 98 spoligotypes and VNTR types were observed with 27 clusters and 71 orphan types. By performing a meta-analysis with previous spoligotyping results, we identified regional and temporal trends in the population structure of M. bovis. For SB0140, the most predominant spoligotype in Argentina, the prevalence percentage remained high during different periods, varying from 25.5-57.8% (1994-2011). By contrast, the second and third most prevalent spoligotypes exhibited important fluctuations. This study shows that there has been an expansion in ancestral lineages as demonstrated by spoligotyping. However, exact tandem repeat typing suggests dynamic changes in the clonal population of this microorganism.

Detection and identification of bovine tuberculosis and its differentiation from micobacteriosis is fundamental during diagnoses. That is why mycobacteria laboratories improvement becomes essential in public health and veterinary medicine services. The objective of the present research is to differentiate Mycobacterium bovis and nontuberculous mycobacterias in isolates cultured from domestic and wildlife species from seven Argentinean provinces during 2004-2008. Differentiation was based on biochemical tests, phenotypic characteristics and M. bovis spolygotyping. Biochemical and phenotypic identification resulted in 20 M. bovis strains, 18 of them were confirmed by spolygotyping, and 34 nontuberculous mycobacteria strains. Thirteen species were characterized and all of them were grouped considering biological risk and pathogenic potential reported in humans and/or animals. Here we have reached advances in tuberculosis and micobacteriosis diagnoses in veterinary medicine. In this area diagnoses are often based on micro and macroscopic observation of the tubercles and skin test results. These advances are not minor as zoonotic tuberculosis is still a public health problem in Latin America.